JP5-106427A, published by the Japan Patent Office in 1993, discloses a technique for regenerating a so-called DPM filter in which a DPM filter for trapping DPM is disposed on an exhaust passage in order to process DPM discharged from a diesel engine, and when a predetermined amount of DPM accumulates in the DPM filter, the temperature of the DPM filter is raised such that the accumulated DPM in the DPM filter is processed by combustion.
Examples of methods for raising the temperature of a DPM filter include a method of increasing the fuel injection amount, a method of performing post-injection following the main injection, and a method of retarding the injection timing.